The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Brush-Less Direct Current (BLDC) motors, also known as electronically commutated synchronous motors, use electronic commutation to control magnetic fields in a stator that cause movement of a rotor. Motor control circuits sense a rotational position of the rotor, herein referred to as the position of the rotor, to control timings of the electronic commutation.
In some BLDC motors, sensors such as of Hall-effect sensors are used to determine the position of the rotor. In contrast, sensorless BLDC motors may use Back-Electro-Motive Force (Back-EMF) detection to determine the position of the rotor while the rotor is moving.
However, during a start-up period in which the rotor is stationary or moving very slowly, Back-EMF is weak, and additional techniques may be used for reliable spin-up of the BLDC motor. One such technique is inductive sense.
Inductive sense determines a position of a magnet according to differences in an inductance of a coil caused by a proximity and a polarity of the magnet relative to the coil. Because a rotor of a BLDC motor acts as a magnet, a motor controller may determine a position of the rotor relative to one or more coils of the BLDC motor by measuring an inductance of the one or more coils.